Highlifts for motor graders are well known and one particular design uses opposed bell cranks secured either side of a grader. U.S. Pat. No. 3,986,563 is an example of such a structure and this structure additionally discloses the use of locking ports in the bell cranks to define further locking positions.
Some designs of opposed bell crank highlift arrangement, some designs have sought to keep the arms well spaced from the main frame of the motor grader to allow viewing in the gap between the bell cranks and the main frame. With this approach, it has been possible to allow for a substantial rotation of the bell cranks and this makes the structure more suitable for ditching and banking to one side of the grader. The high degree of rotation, generally up to around 50.degree., allows the moldboard and the blade to be adjusted to extend to one side of the grader, generally outside of the wheels. In this way, the grader can perform a ditching or banking operation without actually riding on the bank or ditch. This is much safer, as there is generally a flat road bed or flat surface adjacent the ditch.
A slightly different arrangement is disclosed in U.S. Pat. No. 3,739,861 where the rotation of the highlift is more limited, however, the bell cranks of the highlift have been brought in closer to the frame of the grader. By bringing the bell cranks in closer to the grader frame, improved visibility exterior to the bell cranks is provided. This advantage is lost or acts as a disadvantage for ditching or banking operations which require a high degree of rotation.
Although some improved visibility between the bell cranks and the main frame is desirable, it is more preferable to maintain a nonobstructed area generally exterior to the bell cranks.
It is certainly desirable to maintain the bell cranks and related components as small as possible while still providing the necessary degree of rotation either side of the main frame. It is generally believed that a rotation of approximately 50.degree. is satisfactory.